Delintment Lake: Fossil Hunting in Harney County, Oregon

Quick details

Access

Check locally

County

Harney County

State

Oregon

Nearest road

National Forest Development Road 43

Coordinates

43.95140, -119.58250

Geology at Delintment Lake

This spot sits on Olds Ferry Terrane; Snowshoe Formation; Warm Springs/Weberg members, mapped as mudstone, dark gray; fossils: ammonites pelecypods fossils, and calcareous shale that formed roughly 200 to 145 million years ago. Sedimentary layers like these are where fossils are typically preserved, and fresh exposures after rain or in active cuts tend to produce best.

Mapped unit

Olds Ferry Terrane; Snowshoe Formation; Warm Springs/Weberg members

Age

200–145 Ma (Jurassic)

Rock types

mudstone, dark gray; fossils: ammonites pelecypods fossils, and calcareous shale

Elevation

5,540 ft

Geologic mapping via Macrostrat and the underlying state geological survey maps (CC BY 4.0). Bedrock at the surface can vary within a mapped unit.

Best time to visit Delintment Lake

Best months: March to October. Typical highs run 82°F in midsummer and 35°F in midwinter, with winter lows near 14°F.

Climate normals: NOAA 1991-2020 monthlies, PAULINA station (24 mi away), adjusted for elevation.

Land & collecting status

Confirm rules before collecting

Land status here is not confirmed. Verify with the managing agency before collecting — federal, state, and tribal rules differ.

Public-land rules vary by agency, season, and field office. The RockHoundR app pulls live BLM, USFS, NPS, and tribal overlays so you can see exactly which agency manages the ground at this spot.

Sources & verification

Spot details combine the public RockHoundR location dataset, normalized mineral labels, agency land-status checks in the app, and community submissions. Coordinates are approximate until verified in the field.

State guidance last verified: April 1, 2026

• BLM Oregon/Washington — Rockhounding & mineral material
• Oregon Department of Geology and Mineral Industries (DOGAMI)
• Oregon Parks and Recreation Department — beach collecting rules
• Community submissions reviewed against published agency rules

Found at Delintment Lake

Each chip opens all spots that produce that material; the encyclopedia link opens the full ID and field guide.

• Ammonite Fossils
• FossilsEncyclopedia →